Standard and high dynamic range display systems and methods for high dynamic range displays

ABSTRACT

Aspects of the subject technology relate to display circuitry for displaying both standard dynamic range (SDR) and high dynamic range (HDR) content with an HDR display. The subject technology provides a headroom-based transfer function that maintains the contrast of the SDR content whether the display is operated in the SDR or HDR mode.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of co-pending U.S. application Ser. No.16/040,400, filed Jul. 19, 2018, which claims the benefit of U.S.Provisional Patent Application No. 62/664,039, filed on Apr. 27, 2018,both of which are incorporated herein by reference.

TECHNICAL FIELD

The present description relates generally to electronic devices withdisplays, and more particularly, but not exclusively, to standard andhigh dynamic range display systems and methods for high dynamic rangedisplays.

BACKGROUND

Electronic devices such as computers, media players, cellulartelephones, set-top boxes, and other electronic equipment are oftenprovided with displays for displaying visual information.

Content for an electronic device display is typically provided with astandard dynamic range (SDR) of luminance values. The standard dynamicrange (SDR) of luminance values is often consistent with the well-knownsRGB color space or the Recommendation BT.709 (Rec. 709) color space ofthe International Telecommunication Union Radiocommunication Sector(ITU-R), which support luminance values of up to around 100 nits.

However, some electronic device displays, often referred to as highdynamic range (HDR) displays, are capable of providing luminances ashigh as 1000 nits or higher. Increasingly, HDR content is being providedin which the maximum luminance for display is higher than 100 nits, totake advantage of the availability of HDR displays. However, HDRdisplays are often used to display SDR content. When displaying SDRcontent with an HDR display, undesired visual artifacts, such as loss ofcontent visibility and/or an inconsistency in the look of the displayedcontent between different display driving modes, can arise.

BRIEF DESCRIPTION OF THE DRAWINGS

Certain features of the subject technology are set forth in the appendedclaims. However, for purpose of explanation, several embodiments of thesubject technology are set forth in the following figures.

FIG. 1 illustrates a perspective view of an example electronic devicehaving a display in accordance with various aspects of the subjecttechnology.

FIG. 2 illustrates a schematic diagram of exemplary display circuitry inaccordance with various aspects of the subject technology.

FIG. 3 illustrates a flow diagram for displaying standard dynamic rangecontent in a standard dynamic range mode of a high dynamic range displayin accordance with various aspects of the subject technology.

FIG. 4 illustrates a flow diagram for displaying standard dynamic rangecontent in a high dynamic range mode of a high dynamic range display inaccordance with various aspects of the subject technology.

FIG. 5 illustrates a flow diagram for displaying high dynamic rangecontent in a high dynamic range mode of a high dynamic range display inaccordance with various aspects of the subject technology.

FIG. 6 illustrates a flow chart of illustrative operations for a highdynamic range display in accordance with various aspects of the subjecttechnology.

FIG. 7 illustrates another flow chart of illustrative operations for ahigh dynamic range display in accordance with various aspects of thesubject technology.

DETAILED DESCRIPTION

The detailed description set forth below is intended as a description ofvarious configurations of the subject technology and is not intended torepresent the only configurations in which the subject technology may bepracticed. The appended drawings are incorporated herein and constitutea part of the detailed description. The detailed description includesspecific details for the purpose of providing a thorough understandingof the subject technology. However, it will be clear and apparent tothose skilled in the art that the subject technology is not limited tothe specific details set forth herein and may be practiced without thesespecific details. In some instances, well-known structures andcomponents are shown in block diagram form in order to avoid obscuringthe concepts of the subject technology.

The subject disclosure provides electronic devices such as smartphones,tablet computers, media players, desktop computers, set-top boxes,wireless access points, and other electronic equipment that may includedisplays. Displays are used to present visual information and statusdata and/or may be used to gather user input data. A display includes anarray of display pixels. Each display pixel may include one or morecolored subpixels for displaying color images. For example, each displaypixel may include a red subpixel, a green subpixel, and blue subpixel.It should be appreciated that, although the description that followsoften describes operations associated with a display pixel, inimplementations in which each display pixel includes multiple subpixels,the circuitry and operations described herein can be applied and/orperformed, per color, for each subpixel of the display pixel.

Digital pixel values for operating display pixels can have associatedvalues from, for example, 0 to 255. Each display has a characteristicelectro-optical transfer function (EOTF) that determines the luminanceoutput of a display pixel that results from each digital pixel value.Because the EOTF of a display is typically not linear, display controlcircuitry for the display may apply an opto-electronic transfer function(OETF) to content to be displayed by the display, to counter or adapt tothe non-linearity of the display EOTF.

Electronic devices described herein may include high dynamic range (HDR)displays that can generate output luminances of as high as, or higherthan, 1000 nits. However, standard dynamic range (SDR) content, in whichthe full range of available digital pixel values (e.g., integers from0-255) are used to generate luminances in a standard dynamic range thatis smaller than the dynamic range of the display (e.g., less than about100 nits), is often provided for display with an HDR display.

When only SDR content is received for display, an HDR display may applya standard encoding transfer function (e.g., a standardized OETF) togenerate digital pixel values for display. However, when it is desiredto utilize the higher luminance capability of the display (e.g., todisplay HDR content together with or shortly before or after the SDRcontent), the electronic device may scale down the SDR content so thatthe SDR content utilizes a smaller range of digital pixel values (e.g.,a range values from of 0-63). In this way, headroom is created in thedigital pixel values that can be used for displaying HDR content (e.g.,using pixel values from 64-255). In order to maintain the outputluminance when the SDR content is scaled down, the overall luminance ofthe display may be scaled up.

The scaling down of the SDR content may include applying a linearscaling factor (sometimes referred to herein as a headroom factor) tothe SDR content before encoding the SDR content into digital pixelvalues. However, if care is not taken, when the encoding is applied tothe scaled SDR content, various aspects of the front-of-screenappearance of the SDR content can be undesirably changed. For example,the contrast between displayed low and/or medium grey levels in thescaled SDR content can be visibly different from a display of unscaledSDR content, which can be unpleasant to a viewing user.

In accordance with some aspects of the subject disclosure, which aredescribed in further detail hereinafter, systems and methods foroperating a high dynamic range display to consistently display standarddynamic range content are provided. For example, display controlcircuitry may obtain a headroom factor that has been applied to SDRcontent for display, and generate digital pixel values for displayingthe SDR content by applying a transfer function that is dependent on theobtained headroom factor. The transfer function may include variousportions that depend differently on the obtained headroom factor and/ormay be applied to different ranges of the SDR content. The ranges mayhave boundaries that depend on the obtained headroom factor.

It should also be appreciated that headroom-dependent modifications todisplay content and/or pixel luminance can be applied in operationalscenarios other than scenarios in which SDR content is displayed in anHDR mode of an HDR display (e.g., in any operational scenario in whichdisplay content values are scaled or otherwise reduced or increased by aheadroom modification, relative to the range of desired luminances forthose values). The systems and methods described herein, in which atransfer function that is dependent on the headroom modification isapplied, can be beneficial in any of these operational scenarios (e.g.,to preserve the contrast of the displayed content and avoid other visualartifacts as described herein).

An illustrative electronic device having a display is shown in FIG. 1.In the example of FIG. 1, device 100 has been implemented using ahousing that is sufficiently small to be portable and carried by a user(e.g., device 100 of FIG. 1 may be a handheld electronic device such asa tablet computer or a cellular telephone). As shown in FIG. 1, device100 includes a display such as display 110 mounted on the front ofhousing 106. Display 110 may be substantially filled with active displaypixels or may have an active portion and an inactive portion. Display110 may have openings (e.g., openings in the inactive or active portionsof display 110) such as an opening to accommodate button 104 and/orother openings such as an opening to accommodate a speaker, a lightsource, or a camera.

Display 110 may be a touch screen that incorporates capacitive touchelectrodes or other touch sensor components or may be a display that isnot touch-sensitive. Display 110 includes display pixels formed fromlight-emitting diodes (LEDs), organic light-emitting diodes (OLEDs),plasma cells, electrophoretic display elements, electrowetting displayelements, liquid crystal display (LCD) components, or other suitabledisplay pixel structures. In various implementations, any suitable typeof display technology may be used in forming display 110 if desired.Display 110 may be a high dynamic range (HDR) display capable ofemitting light with luminance values between, for example, 0.005 nitsand 1000 nits with a contrast ratio of, for example, 10000:1 or 20000:1.

Housing 106, which may sometimes be referred to as a case, may be formedof plastic, glass, ceramics, fiber composites, metal (e.g., stainlesssteel, aluminum, etc.), other suitable materials, or a combination ofany two or more of these materials.

The configuration of electronic device 100 of FIG. 1 is merelyillustrative. In other implementations, electronic device 100 may be acomputer such as a computer that is integrated into a display such as acomputer monitor, a laptop computer, a somewhat smaller portable devicesuch as a wrist-watch device, a pendant device, or other wearable orminiature device, a media player, a gaming device, a navigation device,a computer monitor, a television, or other electronic equipment.

For example, in some implementations, housing 106 may be formed using aunibody configuration in which some or all of housing 106 is machined ormolded as a single structure or may be formed using multiple structures(e.g., an internal frame structure, one or more structures that formexterior housing surfaces, etc.). Although housing 106 of FIG. 1 isshown as a single structure, housing 106 may have multiple parts. Forexample, housing 106 may have upper portion and lower portion coupled tothe upper portion using a hinge that allows the upper portion to rotateabout a rotational axis relative to the lower portion. A keyboard suchas a QWERTY keyboard and a touch pad may be mounted in the lower housingportion, in some implementations.

In some implementations, electronic device 100 may be provided in theform of a computer integrated into a computer monitor. Display 110 maybe mounted on a front surface of housing 106 and a stand may be providedto support housing (e.g., on a desktop).

FIG. 2 is a schematic diagram of device 100 showing illustrativecircuitry that may be used in displaying images for a user of device 100on pixel array 200 of display 110. As shown in FIG. 2, display 110 mayinclude column driver circuitry 202 that drives data signals (analogvoltages) onto the data lines D of array 200. Gate driver circuitry 204may drive gate line signals onto gate lines G of array 200.

Using the data lines D and gate lines G, display pixels 206 may beoperated to display images on display 110 for a user. In someimplementations, gate driver circuitry 204 may be implemented usingthin-film transistor circuitry on a display substrate such as a glass orplastic display substrate or may be implemented using integratedcircuits that are mounted on the display substrate or attached to thedisplay substrate by a flexible printed circuit or other connectinglayer. In some implementations, column driver circuitry 202 may beimplemented using one or more column driver integrated circuits that aremounted on the display substrate or using column driver circuits mountedon other substrates.

Device 100 may include system circuitry 208. System circuitry 208 mayinclude one or more different types of storage such as hard disk drivestorage, nonvolatile memory (e.g., flash memory or otherelectrically-programmable-read-only memory), volatile memory (e.g.,static or dynamic random-access-memory), magnetic or optical storage,permanent or removable storage and/or other non-transitory storage mediaconfigure to store static data, dynamic data, and/or computer readableinstructions for processing circuitry in system circuitry 208.Processing circuitry in system circuitry 208 may be used in controllingthe operation of device 100. Processing circuitry in system circuitry208 may sometimes be referred to herein as system circuitry or asystem-on-chip (SOC) for device 100.

The processing circuitry may be based on a processor such as amicroprocessor and other suitable integrated circuits, multi-coreprocessors, one or more application specific integrated circuits (ASICs)or field programmable gate arrays (FPGAs) that execute sequences ofinstructions or code, as examples. In one suitable arrangement, systemcircuitry 208 may be used to run software for device 100, such asinternet browsing applications, email applications, media playbackapplications, operating system functions, software for capturing andprocessing images, software implementing functions associated withgathering and processing sensor data, software that makes adjustments todisplay brightness, scales digital display content to generate headroomfor HDR content display, adjusts touch sensor functionality, etc.

During operation of device 100, system circuitry 208 may generate orreceive data that is to be displayed on display 110. The display datamay be received in image pixel values, linear color space values, orother formats. This display data may be processed, scaled, modified,and/or provided to display control circuitry such as graphics processingunit (GPU) 212. For example display frames, including display pixelvalues (e.g., each corresponding to a grey level) for display usingpixels 206 (e.g., colored subpixels such as red, green, and bluesubpixels) may be provided from system circuitry 208 to GPU 212. GPU 212may process the display frames and provide processed display frames totiming controller integrated circuit 210.

System circuitry 208 and/or GPU 212 may, for example, determine that thedigital display data includes only SDR content and may process and/orpass the data to timing controller 210 and instruct display controlcircuitry 214 to operate pixels 206 in a standard dynamic range (SDR)mode. In other operational scenarios, system circuitry 208 and/or GPU212 may determine that the digital display data includes only HDRcontent and may process and/or pass the data to timing controller 210and instruct display control circuitry 214 to operate in an HDR mode(e.g., by increasing the overall luminance of the display, relative tothe SDR mode, for all received display pixel values). In someoperational scenarios, system circuitry 208 and/or GPU 212 may determinethat the digital display data includes SDR content and HDR content, andmay scale down (or otherwise decrease) the SDR content before processingand/or passing the data to timing controller 210 for display in the HDRmode.

Scaling down the SDR content may include generating or receiving ascaling factor by which the overall luminance of the display is to beincreased to switch from the SDR mode to the HDR mode, and applying thatscaling factor as a headroom factor to the SDR content (e.g., bydividing the SDR content by the headroom factor or multiplying the SDRcontent by the inverse of the headroom factor). If the SDR content hasbeen provided in pixel values corresponding to a color space with aknown transfer function already applied (e.g., if a JPEG image in thesRGB color space is provided for display), the inverse of the knowntransfer function may be applied to the SDR content to linearize the SDRcontent before headroom scaling.

Timing controller 210 and/or other portions of display control circuitry214 (and/or GPU 212) may apply an appropriate transfer function to thedigital display data, depending on whether the digital display dataincludes SDR content for display in the SDR mode, HDR content fordisplay in the HDR mode, and/or SDR content for display in the HDR mode.When SDR content is provided for display in the HDR mode (e.g., and theSDR content has been scaled by the headroom scaling factor), thetransfer function may be a non-linear modification of the SDR contentthat is based on the headroom scaling factor. As described in furtherdetail hereinafter, the transfer function may be a piecewiseopto-electronic transfer function or OETF (e.g., having multipleportions each with a particular exponentiation of the headroom scalingfactor and/or each being applied to a range of SDR content values thatis bounded by a value that depends on the headroom scaling factor).

Applying the transfer function generates digital pixel values to beapplied with pixels 206 to generate the desired display light. Timingcontroller 210 provides digital display data (e.g., the digital pixelvalues each corresponding to a grey level for display) to column drivercircuitry 202. Column driver circuitry 202 may receive the digitaldisplay data from timing controller 210. Using digital-to-analogconverter circuitry within column driver circuitry 202, column drivercircuitry 202 may provide corresponding analog output signals on thedata lines D running along the columns of display pixels 206 of array200.

The luminance of the display light that is generated by pixels 206 mayrelate to the digital display data received by column driver circuitry202 by an electro-optical transfer function (EOTF) that is, for example,an intrinsic characteristic of the display. Column driver circuitry 202or other display circuitry may scale the EOTF of the display foroperation in the HDR mode. For example, in an SDR mode of operation forthe display, a digital pixel value of 255 may generate an outputluminance 100 nits. In an HDR mode of operation for the display, thedigital pixel value of 255 may generate an output luminance of 400 nits.In this way, the HDR capabilities of the display can be used to outputluminances above the standard dynamic display range. In this examplescenario, SDR content for display in the HDR mode may be scaled down sothat the desired 100 nits output luminance for a particular pixel can beachieved, even in the HDR mode (e.g., by scaling the 255 value for thatpixel down to a smaller pixel value such as 64). The selection andapplication of the appropriate OETF may help reduce changes in visiblecontrast due to these scalings and may further alter the reduced pixelvalues of some pixels.

Graphics processing unit 212 and timing controller 210 may sometimescollectively be referred to herein as display control circuitry 214.Display control circuitry 214 may be used in controlling the operationof display 110. Display control circuitry 214 may sometimes be referredto herein as a display driver, a display controller, a display driverintegrated circuit (IC), or a driver IC. Graphics processing unit 212and timing controller 210 may be formed in a common package (e.g., anSOC package) or may be implemented separately (e.g., as separateintegrated circuits). In some implementations, timing controller 210 maybe implemented separately as a display driver, a display controller, adisplay driver integrated circuit (IC), or a driver IC that receivesprocessed display data from graphics processing unit 212. Accordingly,in some implementations, graphics processing unit 212 may be consideredto be part of the system circuitry (e.g., together with system circuitry208) that provides display data to the display control circuitry (e.g.,implemented as timing controller 210, gate drivers 204, and/or columndrivers 202). Although a signal gate line G and a single data line D foreach pixel 206 are illustrated in FIG. 2, this is merely illustrativeand one or more additional row-wise and/or column-wise control lines maybe coupled to each pixel 206 in various implementations.

FIGS. 3-5 schematically show how display content to be displayed by HDRdisplay 110 may be processed (e.g., using the components of FIG. 2) toconsistently display SDR content in both SDR and HDR modes of operationfor the display. In particular, FIG. 3 illustrates an operation fordisplaying SDR display content 300 is an SDR mode for display 110.

SDR content 300 may include linear content values for display. In theexample of FIG. 3, SDR content 300 is processed (e.g., by GPU 212 and/ordisplay control circuitry 214) by applying headroom-independent softwaretransfer function 302. Headroom-independent software transfer function302 may be an OETF that encodes SDR content 300 into encoded SDR displaycontent 304 (e.g., digital pixel values) in a way that at leastpartially compensates for hardware transfer function 306 (e.g., anon-linear EOTF) so that SDR display output 308 correlates in thedesired manner (e.g., with the desired luminance and contrast) with SDRdisplay content 300.

Applying hardware transfer function (or EOTF) 306 may be achieved byoperating display pixels 206 to display encoded SDR display content 304.As indicated, OETF 302 is independent of headroom for display of SDRcontent in an SDR mode. OETF 302 may, for example, be a standard OETFsuch as the gamma function of the sRGB or Rec. 709 standards. EOTF 306may be an inverse of OETF 302 or may be different from the inverse ofOETF 302. Applying an EOTF 306 that is different from the inverse ofOETF 302 can generate a particular look (e.g., contrast) for displayedcontent that can be recognizable to a user, and that may be desirable topreserve for the user in different display driving modes (e.g., usingthe operations described below in connection with FIGS. 4-7).

In contrast to FIG. 3, FIG. 4 illustrates operations that may beperformed for displaying SDR content in an HDR mode for display 110. Asshown in FIG. 4, display control circuitry such as display controlcircuitry 214 or GPU 212 may receive headroom-modified SDR content suchas headroom-scaled SDR content 400 (e.g., from system circuitry 208).Headroom-modified SDR content 400 may be digital content for displaywith display pixels 206, the digital content having been modified (e.g.,reduced by a headroom reduction such as by being scaled by a headroomfactor) for high dynamic range operation of the display. For example,headroom-modified SDR content 400 may include linear color space valuesthat span a reduced range (e.g., by application of a headroom factorthat is a multiplicative factor that, when applied, scales the originallinear color space values to reduce the range). A transfer function 402that is based on the headroom modification (e.g., based on the headroomfactor) may be applied to headroom-modified digital content 400 (e.g.,the scaled linear color space values).

Headroom-dependent software transfer function 402 may be an OETF thatencodes headroom-modified SDR content 400 into encoded, modified (e.g.,scaled), corrected SDR display content 404 (e.g., digital pixel values)in a way that at least partially compensates for a modified (e.g.,scaled) hardware transfer function 406 (e.g., a non-linear EOTF such asEOTF 306 that is modified based on the headroom modification applied tothe SDR display content, such as by scaling of the EOTF 306 up by theheadroom factor) so that SDR display output 408 correlates in thedesired manner (e.g., with the desired luminance and contrast) with theluminance, color, and contrast characteristics of SDR display output308, but specific to the content in content 400.

As indicated, OETF 402 is dependent on the headroom modification (e.g.,the scaling factor) applied to headroom-modified SDR display content400. For example, transfer function 402 may include at least oneexponentiation of the headroom factor. The at least one exponentiationof the headroom factor may include a plurality of differentexponentiations of the headroom factor, each of the differentexponentiations associated with a different exponent for the headroomfactor. Display control circuitry 214 and/or GPU 212 may select from thedifferent exponentiations based on a comparison of headroom-scaled SDRdisplay content 400 to a boundary value that depends on the headroomfactor. For example, transfer function 402 may be a piecewise transferfunction in which the headroom factor is exponentiated differently fordifferent ranges of headroom-scaled SDR display content 400, the rangesdefined by boundary values that also depend on the headroom factor.

As shown in FIG. 5, display control circuitry 214 and/or GPU 212 mayapply an additional transfer function 502, that is independent of theheadroom factor, to HDR display content 500 (which may be anotherportion of the digital content that includes SDR content 400) fordisplay using pixels 206. Standard dynamic range content 300 and 400 maybe associated with a maximum luminance. High dynamic range content 500includes at least one value associated with a luminance that is greaterthan the maximum luminance of the standard dynamic range content.

Headroom-independent software transfer function 502 may be an OETF thatis different from OETF 302 and OETF 402, and encodes HDR content 500into encoded HDR display content 504 (e.g., digital pixel values) in away that at least partially compensates for headroom-modified (e.g.,scaled) hardware transfer function 406 (e.g., a non-linear EOTF) so thatHDR display output 508 correlates in the desired manner (e.g., with thedesired luminance and contrast) with HDR display content 500.

FIG. 6 depicts a flow diagram of an example process for displaying SDRcontent and/or HDR content with HDR displays in accordance with variousaspects of the subject technology. For explanatory purposes, the exampleprocess of FIG. 6 is described herein with reference to the componentsof FIGS. 1-5. Further for explanatory purposes, the blocks of theexample process of FIG. 6 are described herein as occurring in series,or linearly. However, multiple blocks of the example process of FIG. 6may occur in parallel. In addition, the blocks of the example process ofFIG. 6 need not be performed in the order shown and/or one or more ofthe blocks of the example process of FIG. 6 need not be performed.

In the depicted example flow diagram, at block 600, first displaycontent such as SDR content 300 having a first luminance range that issmaller than the output luminance range of the display is displayed.Displaying the first display content may include applying transferfunction 302 and operating pixels 206 to display encoded SDR content304.

At block 602, while displaying the first display content, the displaymay be controlled to limit a maximum operating luminance to a maximum ofthe first luminance range. In this way, the display is operated in anSDR mode to display SDR content 300.

At block 604, the display (e.g., display control circuitry 214 and/orGPU 212) may receive second display content. The second display contentmay include SDR content and HDR content.

At block 606, display control circuitry 214 increases the maximumoperating luminance of the display by a headroom increase (e.g., by ascaling factor such as a factor of two, four, six, eight, etc.).

At block 608, system circuitry 208 may apply a headroom reduction (e.g.,by applying an inverse of the scaling factor) to at least a portion ofthe second display content (e.g., the SDR content portion of the seconddisplay content to generate headroom-scaled SDR display content 400).

At block 610, display control circuitry 214 and/or GPU 212 may apply anon-linear modification that is based on the headroom reduction and/orthe headroom increase, (e.g., by applying headroom-dependent softwaretransfer function 402) to at least some of the at least the portion ofthe second display content. The non-linear modification that is based onthe scaling factor may be a piecewise modification of the SDR portion ofthe second display content. The piecewise modification may include anapplication of a plurality non-linear transfer functions, each uniquelybased on the scaling factor (e.g., each including a uniqueexponentiation of the scaling factor). Each of the plurality non-lineartransfer functions is associated with a range that is based on thescaling factor such that the piecewise breakup of the headroom-dependentsoftware transfer function 402 is by ranges that are bounded based acomparison of the content to be displayed with a value that depends onthe headroom scaling factor.

At block 612 display 110 may display the second display content (e.g.,encoded, modified, corrected SDR display content 404), while controllingthe display with the increased maximum operating luminance (e.g., in theHDR mode).

It should be appreciated that display 110 may also apply a non-linearmodification that is independent of the scaling factor (e.g., OETF 502)to another portion of the second display content (e.g., HDR displaycontent 500) prior to displaying the second display content. The otherportion of the second display content (e.g., the HDR portion) includescontent such as one or more pixel values having a luminance that isoutside the first luminance range of the first display content. Thenon-linear modification that is independent of the headroom reduction tothe SDR content (e.g., the scaling factor for the SDR content) isapplied to the other portion of the second display content (e.g., theHDR portion) without applying the headroom reduction (e.g., withoutapplying the inverse of the scaling factor) to the other portion of thesecond display content. In this way, SDR content is displayed with itsintended luminance while allowing headroom for the display of the HDRcontent.

FIG. 7 depicts a flow diagram of another example process for displayingSDR content and/or HDR content with HDR displays in accordance withvarious aspects of the subject technology. For explanatory purposes, theexample process of FIG. 7 is described herein with reference to thecomponents of FIGS. 1-5. Further for explanatory purposes, the blocks ofthe example process of FIG. 7 are described herein as occurring inseries, or linearly. However, multiple blocks of the example process ofFIG. 7 may occur in parallel. In addition, the blocks of the exampleprocess of FIG. 7 need not be performed in the order shown and/or one ormore of the blocks of the example process of FIG. 7 need not beperformed.

In the depicted example process, at block 700, an HDR display such asdisplay 110 is operated in a standard dynamic range mode to displayfirst standard dynamic range content (e.g., SDR display content 300)with a contrast. The contrast of the displayed first standard dynamicrange content may be determined, at least in part, by the application ofboth OETF 302 and EOTF 306.

At block 702, the display is switched into to a high dynamic range mode.Switching the display to the HDR mode may include increasing, by aheadroom factor, the luminance output of all pixels 206 for all pixelvalues (e.g., by scaling the voltage corresponding to a particular pixelvalue by the headroom factor).

At block 704, second standard dynamic range content is received fordisplay by the display in the high dynamic range mode.

At block 706, a modification is applied (e.g., by system circuitry 208or display circuitry 214 or 212) to the second standard dynamic rangecontent (e.g., by applying a headroom scaling factor) to create headroom(e.g., in the digital counts for the pixel values) for display of highdynamic range content. The modification may be a linear scaling.Applying the modification to the second standard dynamic range contentmay generate headroom-scaled SDR display content 400, for example.

At block 708, a correction is applied to the modified second standarddynamic range content (e.g., content 400), based on the headroom, (e.g.,by applying headroom-dependent software transfer function 402 to thesecond standard dynamic range content). The correction may be anopto-electronic transfer function based on an amount of the headroom(e.g., the magnitude of the headroom scaling factor). Theopto-electronic transfer function may be a piecewise function having aplurality of piecewise portions that are differently dependent on theamount of the headroom. The piecewise function defines a plurality ofranges for which each of the plurality of piecewise portions are to beapplied, and each of which has a boundary defined in part by the amountof the headroom. In this way, a contrast of the modified second standarddynamic range content (e.g., the contrast of content 400) may be matchedto the contrast of the first standard dynamic range content (e.g., SDRdisplay content 300).

It should be appreciated that the display may then display (e.g., byoperating pixels 206 using display control circuitry 214) the modifiedcorrected standard dynamic range content with the display in the highdynamic range mode. The display may also display high dynamic rangecontent (e.g., HDR display content 500) concurrently with displaying themodified corrected standard dynamic range content (e.g., content 404)with the display in the high dynamic range mode. The high dynamic rangecontent is displayed without applying the modification or the correctionto the high dynamic range content.

In accordance with various aspects of the subject disclosure, anelectronic device with a display is provided, the display including aplurality of pixels and circuitry electrically coupled with theplurality of pixels. The circuitry is configured to receive digitalcontent for display with the plurality of display pixels, the digitalcontent having been modified by a headroom modification for high dynamicrange operation of the display. The circuitry is further configured toapply a transfer function that is based on the headroom modification toa portion of the digital content.

In accordance with other aspects of the subject disclosure, a method ofoperating an electronic device display having an output luminance rangeis provided, the method including displaying first display contenthaving a first luminance range that is smaller than the output luminancerange of the display. The method also includes, while displaying thefirst display content, controlling the display to limit a maximumoperating luminance to a maximum of the first luminance range. Themethod also includes receiving second display content. The method alsoincludes increasing the maximum operating luminance of the display by ascaling factor. The method also includes applying an inverse of thescaling factor to at least a portion of the second display content. Themethod also includes applying a non-linear modification, that is basedon the scaling factor, to at least some of the at least the portion ofthe second display content. The method also includes displaying thesecond display content, while controlling the display with the increasedmaximum operating luminance.

In accordance with other aspects of the subject disclosure, a method ofoperating a display of an electronic device is provided, the methodincluding operating the display in a standard dynamic range mode todisplay first standard dynamic range content with a contrast. The methodalso includes switching the display to a high dynamic range mode. Themethod also includes receiving second standard dynamic range content fordisplay by the display in the high dynamic range mode. The method alsoincludes applying a modification to the second standard dynamic rangecontent to create headroom for display of high dynamic range content.The method also includes applying a correction to the modified secondstandard dynamic range content, based on the headroom, to match acontrast of the modified second standard dynamic range content to thecontrast of the first standard dynamic range content.

Various functions described above can be implemented in digitalelectronic circuitry, in computer software, firmware or hardware. Thetechniques can be implemented using one or more computer programproducts. Programmable processors and computers can be included in orpackaged as mobile devices. The processes and logic flows can beperformed by one or more programmable processors and by one or moreprogrammable logic circuitry. General and special purpose computingdevices and storage devices can be interconnected through communicationnetworks.

Some implementations include electronic components, such asmicroprocessors, storage and memory that store computer programinstructions in a machine-readable or computer-readable medium(alternatively referred to as computer-readable storage media,machine-readable media, or machine-readable storage media). Someexamples of such computer-readable media include RAM, ROM, read-onlycompact discs (CD-ROM), recordable compact discs (CD-R), rewritablecompact discs (CD-RW), read-only digital versatile discs (e.g., DVD-ROM,dual-layer DVD-ROM), a variety of recordable/rewritable DVDs (e.g.,DVD-RAM, DVD-RW, DVD+RW, etc.), flash memory (e.g., SD cards, mini-SDcards, micro-SD cards, etc.), magnetic and/or solid state hard drives,ultra density optical discs, any other optical or magnetic media, andfloppy disks. The computer-readable media can store a computer programthat is executable by at least one processing unit and includes sets ofinstructions for performing various operations. Examples of computerprograms or computer code include machine code, such as is produced by acompiler, and files including higher-level code that are executed by acomputer, an electronic component, or a microprocessor using aninterpreter.

While the above discussion primarily refers to microprocessor ormulti-core processors that execute software, some implementations areperformed by one or more integrated circuits, such as applicationspecific integrated circuits (ASICs) or field programmable gate arrays(FPGAs). In some implementations, such integrated circuits executeinstructions that are stored on the circuit itself.

As used in this specification and any claims of this application, theterms “computer”, “processor”, and “memory” all refer to electronic orother technological devices. These terms exclude people or groups ofpeople. For the purposes of the specification, the terms “display” or“displaying” means displaying on an electronic device. As used in thisspecification and any claims of this application, the terms “computerreadable medium” and “computer readable media” are entirely restrictedto tangible, physical objects that store information in a form that isreadable by a computer. These terms exclude any wireless signals, wireddownload signals, and any other ephemeral signals.

To provide for interaction with a user, implementations of the subjectmatter described in this specification can be implemented on a computerhaving a display device as described herein for displaying informationto the user and a keyboard and a pointing device, such as a mouse or atrackball, by which the user can provide input to the computer. Otherkinds of devices can be used to provide for interaction with a user aswell; for example, feedback provided to the user can be any form ofsensory feedback, such as visual feedback, auditory feedback, or tactilefeedback; and input from the user can be received in any form, includingacoustic, speech, or tactile input.

Many of the above-described features and applications are implemented assoftware processes that are specified as a set of instructions recordedon a computer readable storage medium (also referred to as computerreadable medium). When these instructions are executed by one or moreprocessing unit(s) (e.g., one or more processors, cores of processors,or other processing units), they cause the processing unit(s) to performthe actions indicated in the instructions. Examples of computer readablemedia include, but are not limited to, CD-ROMs, flash drives, RAM chips,hard drives, EPROMs, etc. The computer readable media does not includecarrier waves and electronic signals passing wirelessly or over wiredconnections.

In this specification, the term “software” is meant to include firmwareresiding in read-only memory or applications stored in magnetic storage,which can be read into memory for processing by a processor. Also, insome implementations, multiple software aspects of the subjectdisclosure can be implemented as sub-parts of a larger program whileremaining distinct software aspects of the subject disclosure. In someimplementations, multiple software aspects can also be implemented asseparate programs. Finally, any combination of separate programs thattogether implement a software aspect described here is within the scopeof the subject disclosure. In some implementations, the softwareprograms, when installed to operate on one or more electronic systems,define one or more specific machine implementations that execute andperform the operations of the software programs.

A computer program (also known as a program, software, softwareapplication, script, or code) can be written in any form of programminglanguage, including compiled or interpreted languages, declarative orprocedural languages, and it can be deployed in any form, including as astand alone program or as a module, component, subroutine, object, orother unit suitable for use in a computing environment. A computerprogram may, but need not, correspond to a file in a file system. Aprogram can be stored in a portion of a file that holds other programsor data (e.g., one or more scripts stored in a markup languagedocument), in a single file dedicated to the program in question, or inmultiple coordinated files (e.g., files that store one or more modules,sub programs, or portions of code). A computer program can be deployedto be executed on one computer or on multiple computers that are locatedat one site or distributed across multiple sites and interconnected by acommunication network.

It is understood that any specific order or hierarchy of blocks in theprocesses disclosed is an illustration of example approaches. Based upondesign preferences, it is understood that the specific order orhierarchy of blocks in the processes may be rearranged, or that allillustrated blocks be performed. Some of the blocks may be performedsimultaneously. For example, in certain circumstances, multitasking andparallel processing may be advantageous. Moreover, the separation ofvarious system components in the embodiments described above should notbe understood as requiring such separation in all embodiments, and itshould be understood that the described program components and systemscan generally be integrated together in a single software product orpackaged into multiple software products.

The previous description is provided to enable any person skilled in theart to practice the various aspects described herein. Variousmodifications to these aspects will be readily apparent to those skilledin the art, and the generic principles defined herein may be applied toother aspects. Thus, the claims are not intended to be limited to theaspects shown herein, but are to be accorded the full scope consistentwith the language claims, wherein reference to an element in thesingular is not intended to mean “one and only one” unless specificallyso stated, but rather “one or more.” Unless specifically statedotherwise, the term “some” refers to one or more. Pronouns in themasculine (e.g., his) include the feminine and neuter gender (e.g., herand its) and vice versa. Headings and subheadings, if any, are used forconvenience only and do not limit the subject disclosure.

The predicate words “configured to”, “operable to”, and “programmed to”do not imply any particular tangible or intangible modification of asubject, but, rather, are intended to be used interchangeably. Forexample, a processor configured to monitor and control an operation or acomponent may also mean the processor being programmed to monitor andcontrol the operation or the processor being operable to monitor andcontrol the operation. Likewise, a processor configured to execute codecan be construed as a processor programmed to execute code or operableto execute code

A phrase such as an “aspect” does not imply that such aspect isessential to the subject technology or that such aspect applies to allconfigurations of the subject technology. A disclosure relating to anaspect may apply to all configurations, or one or more configurations. Aphrase such as an aspect may refer to one or more aspects and viceversa. A phrase such as a “configuration” does not imply that suchconfiguration is essential to the subject technology or that suchconfiguration applies to all configurations of the subject technology. Adisclosure relating to a configuration may apply to all configurations,or one or more configurations. A phrase such as a configuration mayrefer to one or more configurations and vice versa.

The word “example” is used herein to mean “serving as an example orillustration.” Any aspect or design described herein as “example” is notnecessarily to be construed as preferred or advantageous over otheraspects or design.

All structural and functional equivalents to the elements of the variousaspects described throughout this disclosure that are known or latercome to be known to those of ordinary skill in the art are expresslyincorporated herein by reference and are intended to be encompassed bythe claims. Moreover, nothing disclosed herein is intended to bededicated to the public regardless of whether such disclosure isexplicitly recited in the claims. No claim element is to be construedunder the provisions of 35 U.S.C. § 112, sixth paragraph, unless theelement is expressly recited using the phrase “means for” or, in thecase of a method claim, the element is recited using the phrase “stepfor.” Furthermore, to the extent that the term “include,” “have,” or thelike is used in the description or the claims, such term is intended tobe inclusive in a manner similar to the term “comprise” as “comprise” isinterpreted when employed as a transitional word in a claim.

What is claimed is:
 1. A method of operating an electronic devicedisplay having an output luminance range, the method comprising:displaying first display content having a first luminance range that issmaller than the output luminance range of the display; receiving seconddisplay content; increasing an operating luminance of the display by ascaling factor; applying an inverse of the scaling factor to at least aportion of the second display content to generate headroom-scaleddisplay content; applying a non-linear modification, that is based onthe scaling factor, to at least some of the at least the portion of thesecond display content; and displaying the second display content, whilecontrolling the display with the increased operating luminance.
 2. Themethod of claim 1, further comprising: while displaying the firstdisplay content, controlling the display to limit the operatingluminance to a maximum of the first luminance range.
 3. The method ofclaim 1, wherein the second display content includes standard dynamicrange (SDR) content and high dynamic range (HDR) content with the SDRcontent being displayed with intended luminance while allowing headroomfor display of the HDR content.
 4. The method of claim 1, furthercomprising: applying a non-linear modification that is independent ofthe scaling factor to another portion of the second display contentprior to displaying the second display content.
 5. The method of claim4, wherein applying the non-linear modification that is independent ofthe scaling factor to the other portion of the second display contentcomprises applying the non-linear modification without applying theinverse of the scaling factor to the other portion of the second displaycontent.
 6. The method of claim 4, wherein the non-linear modificationthat is based on the scaling factor comprises a piecewise modificationof the at least some of the at least the portion of the second displaycontent, the piecewise modification including a plurality non-lineartransfer functions, each uniquely based on the scaling factor.
 7. Themethod of claim 6, wherein each of the plurality non-linear transferfunctions is associated with a range that is based on the scalingfactor.
 8. The method of claim 4: wherein applying the non-linearmodification that is independent of the scaling factor to the otherportion of the second display content comprises applying the non-linearmodification without applying the inverse of the scaling factor to theother portion of the second display content; and wherein the otherportion of the second display content comprises content having aluminance that is outside the first luminance range of the first displaycontent.
 9. A method of operating a display of an electronic device, themethod comprising: operating the display in a standard dynamic rangemode to display first standard dynamic range content with a contrast;switching the display to a high dynamic range mode; receiving secondstandard dynamic range content for display by the display in the highdynamic range mode; applying a modification to the second standarddynamic range content to create headroom for display of high dynamicrange content; and applying a correction to the modified second standarddynamic range content, based on the headroom, to match a contrast of themodified second standard dynamic range content to the contrast of thefirst standard dynamic range content.
 10. The method of claim 9, furthercomprising displaying the modified corrected standard dynamic rangecontent with the display in the high dynamic range mode.
 11. The methodof claim 10, further comprising displaying high dynamic range contentconcurrently with displaying the modified corrected standard dynamicrange content with the display in the high dynamic range mode.
 12. Themethod of claim 11, wherein displaying the high dynamic range contentcomprises displaying the high dynamic range content without applying themodification or the correction to the high dynamic range content. 13.The method of claim 11, wherein the modification comprises a linearscaling.
 14. The method of claim 13, wherein the correction comprises anapplication of an opto-electronic transfer function that depends on anamount of the headroom.
 15. The method of claim 14, wherein theopto-electronic transfer function comprises a piecewise function havinga plurality of piecewise portions that are differently dependent on theamount of the headroom.
 16. The method of claim 15, wherein thepiecewise function defines a plurality of ranges for which each of theplurality of piecewise portions are to be applied, and each of which hasa boundary defined in part by the amount of the headroom.
 17. The methodof claim 9, wherein switching the display to a high dynamic range modecomprises increasing, by a headroom factor, a luminance output of pixelsof the display.